At the moment, I believe there are very few designs capable of slipstream. The hull of most starships isn't "streamlined" enough for the version that Starfleet uses. I'm afraid I can't recall the reasoning or the nature of quantum slipstream, but it has certainly been discussed. The Typhon Pact novels Plagues of Night and Raise the Dawn are among those in which discussion of the necessary features for slipstream adaptation takes place.

The Intrepid-class had to be refitted in order to make it fully and safely slipstream-compatible. We have the Merian-class science vessels (24th Century Mirandas with triangular hulls and a tendency to come a cropper), the Mulciber-class (long and thin, triangular primary hull), Theophrastus-class (sleek, possibly built specifically for slipstream use?) and the one-of-a-kind Galen-class.

I'm guessing that Nova-class vessels could probably be refitted, if Merians and Intrepids can?

Thanks, thats a really comprehensive opening reply; I was actually wondering about the Prometheus class and Akira class specifically - at least the Prometheus class is angular, and it's technology is more advanced than Intrepid-era - so I'm guessing it would be one of the slipstream compatible vessels.

The Akira class on the other hand, I don't know. Round saucers don't seem to get a lot of love with quantum slipstream.... I guess even such advanced vessels as the Galaxy class have been rendered obsolete

There's also some information about the mechanics and the vessel's required frontal geometry in Greater than the Sum and Zero Sum Game, I believe? Basically, sleek and pointy is the way to slipstream velocities - As long as one has the benamite crystals, chroniton integrators and other thingummybobs.

I keep hoping that we'll see a Sovereign-class retrofitted with quantum slipstream drive. I'm sure they wouldn't need too much jiggery-pokery to achieve it?
Where as something like a Nebula or Galaxy-class is probably far to blunt and wide to carry it off?

Slipstream tunnels are quite narrow, hence starships need to be narrow and long for optimal passage. It's possible to generate wider tunnels but the power requirement is huge and not particularly efficient.

Slipstream tunnels are quite narrow, hence starships need to be narrow and long for optimal passage. It's possible to generate wider tunnels but the power requirement is huge and not particularly efficient.

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It's not so much that the tunnels are narrow by nature and the shape of the ships evolved to follow that.
It's that they discovered that creating a narrower tunnel is more power efficient and creates less stress on the hull.

In STO, every single playable ship is capable of attaining quantum slipstream velocities, for game-mechanical reasons. That includes the NX-class light cruiser and Type 8 shuttle craft. :-)

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But then STO is 20+ years away from the current time period in the novels (not to mention being a parallel reality too!), so you could posit that by the 2400's, QS tech has evolved to the point where hull streamlining isn't needed anymore. Maybe it gets out-engineered, like the Intrepid-class's variable-geometry warp nacelles...

Also, the slipstream in STO is quite limited for most ships. They explicitly need some other means of travel to actually reach the Solanae Dyson Sphere in the Delta Quadrant, something the novelverse slipstream ships could do with just their onboard equipment.

They explicitly need some other means of travel to actually reach the Solanae Dyson Sphere in the Delta Quadrant, something the novelverse slipstream ships could do with just their onboard equipment.

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Until you either hit tier 1 on the Dyson reputation system or youe fleet (if you are in one) progresses far enough in developing their spire then you can just transwarp to the sphere which only take a few seconds no matter where in the galaxy you are.

looking at general profile V size, I would say the Sovereign class is streamlined enough for slipstream, it has a relatively small forward aspect profile for a ship of it's size and the Achilles has been described as much larger (at least my impression is it's huge).

Galaxy and Nebulas... that's tricky, they're not really "space aerodynamic" like Voyager or the Vesta, but since when has space physics ever reflected the capabilities of a ship? I'd say it's entirely possible the Galaxies and older can't endure slipstream for some other reason, possibly because of the subspace damaging warp tech they were designed for? The newer ships Intrepid and up didn't suffer from these issues.

The idea that the Breen prototype ship being symmetrical may merely be because of how atypical the breen starship superstructures are.

Did the books ever mention whether or not slipstream technology was something the Federation had developed prior to Voyager's return from the Delta Quadrant?

I remember some discussion of this quite some time ago but not how the conversation concluded. On one hand, the first sustainable slipstream that I recollect we've seen is from Voyager's "Hope and Fear", but I don't know off the top of my head if this episode occurred before or after Voyager lost access to the Hirogen comm network that had allowed it to link back to Starfleet. On the other hand, Voyager returned to Earth a very short time before the Vesta- and Meerian-class ships came into service, suggesting that either Starfleet had been working on slipstream for long enough to put these classes into production, or these were pre-existing designs that just happened to be wholly compatible with the slipstream tech that Voyager returned from the DQ with.

Regarding the slipstream tunneling effect itself, I had been of the impression that it had more to do with the deflector array systems than it did the ship's warp drive. I am wondering if there's an in-universe explanation (Trektechplanation?) on why the slipstream-utilizing starship classes have these uber-long warp nacelles.

The Breen prototype's frame had to be gutted and completely rebuilt because it wasn't streamlined enough. The leading designer suspected the Breen were chosen to construct such a ship because their designs were the most unsuitable. Their failure would've damaged their position in the Pact and given the then-hawkish Gorn and Romulans a better position. The prototype had to be streamlined to make QSD work. (Zero Sum Game)

The Vesta- and Merian-classes could've been constructed while Voyager was still in the DQ. Because of the resumed communication in later VOY seasons, it is conceivable they sent the specs for QSD to Starfleet. Starfleet may have been working on the technology before and now received the means to realize it. Coaxial warp drive was innovative as well when encountered by Voyager but Federation scientists were already aware of the option. The theories of advanced engines may exist already.

Or, Starfleet simply scrambled to put these ships on the drawing board and into producation ASAP. Remember, it took post-war Earth less than five years from the Phoenix to launch the S.S. Conestoga. (Federation: The First 150 Years)

Markonian, was the Breen's prototype destroyed in ZSG? Or just damaged but able to be repaired? I don't know where the slipstream tech level is among the Typhon Pact entities.

That's a good point that Starfleet was probably already working on slipstream before Voyager returned home. It would seem to be the most likely explanation, given that Voyager was only in regular communication with Starfleet scant months before "Endgame". IIRC, the Meerian-class was introduced in 2377, the same year Voyager returned from the DQ, so I am inclined to think that this (and the Vesta) was already on the drawing boards prior to any slipstream information from Voyager.

Do we know if Starfleet's done anything with the coaxial warp drive tech?

Another wrinkle to this (albeit a very minor one, admittedly) is how the Federation's development of quantum slipstream drive affected their relationship with the Silgov free remnant (Small World). The proposed partnership (or the seeds of a diplomatic relationship) involved the Silgov's advanced propulsion systems being brought to the table. With the advent of slipstream, they might feel as though they have nothing to offer.

Unless data from the Silgov in fact aided Starfleet in perfecting the slipstream drive?

Since the relationship with the Koas was followed up on, I'd like to know what happened with the Silgov.

Has there been mention in the novels as to whether or not the Sovereign-class can utilize slipstream drive? If I remember correctly, that class is right about the same size as the Vesta-class, and very similar in configuration.

Has there been mention in the novels as to whether or not the Sovereign-class can utilize slipstream drive? If I remember correctly, that class is right about the same size as the Vesta-class, and very similar in configuration.

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I don't recall any such mention. (Although my memory is hardly the best.)

It was mentioned at the end of Peaceable Kingdoms that Enterprise would need upgrades before heading out on her new exploration mission. They didn't specifically mention slipstream, but I am curious to see if she has it in the next TNG novel.